This trial is a multicenter, open-label and prospective randomized controlled study to compare 1-year outcomes of uncomplicated type B intramural hematoma (IMH) patients undergoing thoracic endovascular aortic repair (TEVAR) plus optimal medical therapy (OMT) with that of those undergoing OMT alone. The primary objective is to test the hypothesis that 1-year aortic-related adverse events are lower in TEVAR plus OMT group than that in OMT alone group. The secondary objective is to test the hypothesis that 1-year all-cause mortality, aortic-related mortality and re-intervention are lower in TEVAR plus OMT group than that in OMT alone group.

Intervention group (TEVAR plus OMT): patients will undergo TEVAR besides strict control of blood pressure and heart rate and pain management as mentioned above. According to the preoperative imaging, the potential risk location of the aortic dissection or rupture and the extent of lesion involvement are evaluated, and the appropriate anchoring zone is selected to ensure a sufficient anchorage area of more than 15 mm. If the distance between the potential accident site and the left subclavian artery (LSA) is less than 15 mm, LSA will be covered to obtain sufficient anchoring area. LSA revascularization will be performed by chimney technique or hybrid operation, depending on the choice of the surgeon. The left femoral artery is punctured or cut, the artery sheath is inserted, and the pigtail catheter is inserted into the ascending aorta along the sheath. Next, the aortic covered stent was implanted reverse through the femoral artery under the guidance of the wire. When the stent was released, rapid pacing or intravenous antihypertensive drugs was used to ensure that the blood pressure was lower than 90 mmHg. After stent implantation, re-angiography to confirm the stent location and blood flow, which will indicate whether the operation was successful or not. After all above, the patients will be observed in the hospital for at least 3 days. Controls of the blood pressure and heart rate and relief of the symptoms will meet the discharge criteria.

Conservative group: all patients are under strict control of their blood pressure and heart rate with the guidelines-recommend drugs during hospitalization, including β receptor antagonists with or without other types of antihypertensive drugs if patients can tolerate. The target blood pressure is that systolic blood pressure fluctuates between 100-120 mmHg in the acute and sub-acute phase and blood pressure <130/80 mmHg in the chronic phase. The target heart rate should be limited to 60 bpm in the acute and sub-acute phases. Additionally, pain-releasing drugs ought to be prescribed when needed. Discharge criteria include control of the blood pressure and heart rate and relief of the symptoms.

Inclusion Criteria:

1. Age >18 years;
2. Be confirmed as Stanford type B IMH by aorta computed tomography;
3. From onset to first clinical attach <90 days;
4. The subject or legal guardian understands the nature of the study and agrees to its;
5. provisions on a written informed consent form;
6. Availability for the appropriate follow-up visits during the follow-up period;
7. Capability to follow all study requirements.

Exclusion Criteria:

1. Persistent or recurrent pain despite full medication,;
2. Hemodynamic instability;
3. Signs of rupture (periaortic hemorrhage);
4. Depth of ULP > 10 mm;
5. Aortic diameter > 55 mm;
6. ULP around with calcification;
7. Previous history of aortic-related procedures;
8. Blunt thoracic aortic injury;
9. Iatrogenic aortic injury;
10. Inherited diseases: Turner syndrome, Marfan syndrome, Ehlers-Danlos syndrome, Loeys Dietz syndrome etc.;
11. Aortitis: Giant cell arteritis, Takayasu arteritis etc.;
12. Patients with malignant tumor whose life expectancy is less than 1 year;
13. Intolerance to endotracheal intubation and general anesthesia;
14. Pregnant women.